US2265941A - Saponification of resin acids - Google Patents

Description

Patented Dec. 9, 1941 American Cyanamid Company, New York, N. Y., .a corporation of Maine No Drawing. Application May 17, 1939,

' Serial No. 274,107

9 Claims. (01. 260-105) This invention relates to the saponification of resin acids such as abietic acid with aqueous solutions of alkalies capable of saponifying the same such as sodium or potassium hydroxide,

sodium or potassium carbonate and the like.

In its more specific aspects the invention relates particularly to the production of sizing materials by the saponification of wood or gum.

rosin or similar materials containing abietic acid or other resin acids or their anhydrides with aqueous solutions of saponifying alkalies such as sodium hydroxide or sodium carbonate solutions.

The production of dry rosin sizeis usually carried out by adding an aqueous solution of sodium hydroxide. or sodium carbonate tomolten rosin with vigorous agitation.

sodium hydroxide equal to about 12% of the weight of the resinous material is used'as a;

40-75% aqueous solution, or a correspondingly greater amount of sodium carbonate may be employed. In some cases a free rosin size containing unsaponified rosin is desired, andin this case correspondingly smaller amounts of alkaliesare used. a

The customary method employed in saponifying resin acids consists in melting the rosin or other material and adding the saponifying alkali solution with vigorous agitation of the mixture. This method is simple and inexpensive, but difficulties are frequently encountered by reason of thickening or gelation of the batch to a stage where it is so difiicult to agitate that completereaction between the alkali and the resin acids cannotbe obtained. This formation of indispersible gels is particularly imminent in the last stage of the process, where most but not'all of the saponifying alkali has reacted with the resin acids. In such a case the final product will contain free alkali which is likely to absorb moisture and cause caking in the finished material.

coloration or spontaneous combustion durin storage and shipment of the product.

One of the principal objects of the present invention is the provision of a method of saponifying resin acids with alkaline solutions in which the formation of indispersiblegels is substantially avoided and substantially complete neutralizationof the saponifying alkali is obtained. I have found that the phenomenon of gel formation is a function 01' the water content of the mixture of resin acids and alkali in the saponificationkettle, which, in turn, is dependent upon thetem- When a completely saponified rosin size is desired a quantity. of

Thepresence of free alkali in admixture with freeresin acids also creates a serious hazard of dissolutions under conditions such that the water content of the reaction mixture .is maintainedperature of the reaction mixture and'the-rate at which the saponifying alkali solution is-added. I have also found,as a'principal feature of the invention, that there isa' definite limit of moisture content below which substantial l formation is avoided, and that difficulties due to gelation canbe overcome by'maintaining the mois-; ture content of the batch below this limitat all times.

The problem of gelation isfalso intimately related to the-ratio of saponified to unsaponified resin acids in the reaction mixture, as is shownby the factthat extensive gel formation is usually encountered only during the lastistages 'ofthe reaction when the amount of "saponified acid is high and the amount ofunsaponified and unsaponifiable material in the batch is relatively low. Thus, ior example, in the manufacture of dry rosin 'size it is customary to saponify wood-- or gum rosin which consists of about 91% resinacids and 9% unsaponifiable matter, andin thisprocess there is'usuallyno trouble from gel iormationuntil after about of the rosin acids have been saponified; While; have found that gel formation duringthe last stages o f the cook is initiated by excessive moisture content,

and probably; in localized areas .ofthe batch, it

is probable that the subsequent thickening of the batch is due to the scarcity 'oi' unsaponified material present. It is another object of the invention to carry out at leastthe last stages of the reac-' tion in the presence of substantial quantities of an unsaponifiable diluent which is soluble in the resin acids and compatible with the soaps thereof, as lhave ,found that such a diluent will're-- duce thetendency of the batch to set up under the influence of any gel that may beformed.

. The process of my invention thereforeinvolves the saponification of resin acids with alkaline atall times below a .certain'figure, above which extensive gel formation may be encountered. In

the saponification of wood andgum rosin thisv figure represents amoisturecontent off about 5% of the weight of the batch; .i. e., the batch should not contain more than 5% of moisture -at-any. time during the. cook. This is also :true iorabietic. acidandother' similar resin acids which give. rise to gel formation. It isalso desirable that,

localized areas in the batch'should not contain much more, than 5%.of moisture, but this condition is not absolutely essentialin practicing theinvention and is, infact, very dificult to attain-unless very consentrated solutionsfof alkalies.

are employed. When the moisture content of the batch is maintained well below and a dilute solution of alkali is added the formation of a small amount of gel can sometimes be noted in the area where the saponifying alkali solution is poured in, but this gel is easily dispersed by rapid agitation of the batch.

The water content of the mixture undergoing saponification is most easily maintained at a low figure by first heating the rosin or other material. to temperatures sufficiently high to insure rapid volatilization of water therefrom and then adding the saponifying alkali solution at arate not substantially greater than the rate. oifwater evolu= tion. I have found that temperatures ofl50-'-I80' C. are most suitable for this purpose. It should be noted that water may be present-in the-batch from at least two sources, first the relatively large quantity of water constituting a part of. the saponifying alkali solution and secondly the small quantityof chemical water formedby re action between the caustic-: and the: organic c'ar'-- boxylic acids. The alkali solution is preferably preheated and should be added so slowly that the water from; thesetw'o sources is-vol'atilized at least as fast-as the rate of water addition and formationthe reactionmixture. When this is donethe formation of substantial quantities of indispersible gels is inhibited.

While the process of theinvention; including the addition of unsap'oniflablediluents prior to the completion thereof; isfsuitable for the production of resin acidsoaps in anyform it isparticularly advantageous in operations in which the reaction product is to bemaintained in liquid format elevated temperaturesfor substantialpe riods of time. This condition occurs; for ex=- ample; when the'liquid product is to bepassed over or'between chilled rollers or otherwise solid ifile'd' in films so' that a flaked product isobtained; Under these conditions the addition of an unsaponifiable diluent such' as d-lim'onene (B; P. 175 0.); dipentene (BE P, 175 Gil, terpinenes (B; P. 173-181 (3;), pinenes (Bi Pi 1 55-1'63".') and the like; which are soluble-in the resin acids' and compatible with their soaps; is particularly valuable, for-it also producesa more fiui'd size and permitsflaking at lower temperatures. Even without the diluent; however, a resin size of such low moisture content as is obtainedby the process of, my" invention canbe maintained ina molten condition for long periods of time without danger of gelation and thickening of the batch.

In the foregoingdescriptionthe invention has been referred to interms'ofbatch processes, but its principles are by no means limited to this method of operating. on the contrary, these features are of equal if not greater utility in conbe understood, however, that although these examples describe some of the more limited aspects of the invention they are given primarily for purposes of illustration and that the invention in its broader aspects is not limited thereto.

Example 1 800 parts of N-wood rosin were melted and maintained at substantially 165 C. 80 parts of solid technical caustic soda were dissolved in water to make a 75% solution at 165 C. The caustic solution was then added uniformly to the melted rosin with stirring over a period of ten; minutes. This rate of caustic addition was 'sufiicient to avoid the formation of undesirable tated, the temperature oi. the rolls andthezspeed,

of rotating being such. that adequate solidification of the product would take place while. in contact with the rolls. A doctor'bl'adewas provided to remove the solidified flake. Flaking continued for approximately ten. minutes during 5 which time half of'thereaction; product was. disposed of- To. the remaining quantity in the. reactionvessel, 400 'parts;of.'N-wood rosin at a. temperature of 165' C..were addedsand departs of causticas a 75% aqueous solution at 165" C: were I slowly introducedover: a periodoffive minutes,

while permitting: the 'waterto escape so. thatzthe content thereof was always bclow5%. The reaction product-was maintained in'the; kettle, with agitation for another test period: of fifteen minm.- utes. During'this time,.no:undesirable gel formareaction product.

' the kettle and 40 parts of caustic as a 75%i-aque tinuoussaponification processes, in" which resinacids and alkali solutions. are continuously or intermittently addedand mixed in one part of a reaction system while the finished soap is withdrawn from another part. Such continuous processes require themaintenance of reactionaddition the moisture content of the soap can be maintained at all times below 5%. and thus the formation of indispersible gels is inhibited.

The: invention will be illustrated ingreater detail by the following specific examples. It should By suitably controlling the temperature and rate of alkali ous solution at the same temperature as before,

the rate of alkali addition being such that: the total water content of the reaction mixturewas: After the caustic wasar maintained below 5%. added, the batch was again held for a period of substantially fifteen minut'eswithout the formation of undesirable quantities of gel Flaking was thenbegun and in twentyminutes the entire batch had been satisfactorily flaked. T

The entire operation took substantially 2 hours and" during this time the rosin size itself hadbeen held in a liquid condition for nearly two hours without any sign of setting up or undesirable quantities of gel. 1 I g The flakes themselves were of excellent appearance; golden yellow and from ,4 to /2 inch in-largest'dimension. The solubilityof the flaked.

Example 2 In this case, the total causti'ccusedwas substantially 14% of the weight of v the N-WODd. rosin, added to the melted rosin as a solution at the same temperature as above. The rateofrad dition of the caustic solution was slow enough to prevent the total quantity of water present in the reaction mixture from rising above 4%. The caustic addition period and a testholding period after the caustic addition amounted to approximately 45 minutes. During this time, no undesirable quantities of indispersiblegel was noted. The liquid reaction product was then flaked as in Example 1 except that the entire batch was flaked continuously. The two products were substantially the same except that the one of this example contained substantially no free rosin due to the larger quantity of caustic.

Example 3 This was a batch type of run using G-gum rosin. The caustic soda used was 10% of the weight of the rosin and was added as a 75% solution. The caustic and rosin were combined as above, the caustic solution being added uniformly over a twenty minute period so as to maintain the water content of the reaction mixture below Following the caustic addition, the batch was held for a test period of thirty minutes, while stirring, without the formation of any undesirable quantities of indispersible gel. It was observed in this example that the molten size was somewhat more viscous than when N-wood rosin was used and that the reaction started more slowly.

Example 4 At this point, it was desired to vary the rate of addition of the caustic solution so that the water content of the reaction mixture would rise above 5%. The 14% of caustic and rosin were reacted under the conditions of Example 3 above, up to the time that caustic equivalent to by weight of the rosin had been added slowly, so as to prevent the quantity of water in the reaction product from rising above 5%. No trouble was experienced and no undesirable quantities of indispersible gel were formed. The remaining quantity of caustic was added to the reaction product quickly, with the result that the fusion became so viscous that further agitation was impossible, due to the formation of undesirable quantities of indispersible gel.

Example 5 This run was a repetition of Example 4 except that after adding caustic equivalent to 10% of the rosin, an addition of 2% of dipentene was made before the remaining quantity of caustic was added. Upon adding the remainder of the caustic as in Example 4, no difllculty was experienced due to the fact that the unsaponiflable dipentene acted as a diluent and made the other- This was a repetition of Example 5 without resorting, however, to the use of dipentene but adding the entire quantity of caustic slowly so as to maintain the total water content of the reaction mixture well below 5% and over a period longer than in Example 5. No undesirable quantities of indispersible gel were noted. The flake product was satisfactory.

The behavior of N-wood rosin appears to'be somewhat diiferent from G-gum' r'osin in that it reacts more readily'and forms a less viscous molten product. Since their acid numbers'are notgreatly' different, the variation must arise more from the differences in the nature of the components or in their relative proportions rather than from' their-aggregate amounts. Consequently, the invention is not to be restricted to the examples given, which aremerely illustrative but various modifications may be practiced, the details of procedure being dependent, of course, upon the materials used.

-What I claim is: I

1. A method of saponifying resin acids with alkaline solutions while avoiding gel formation which comprises heating said acids to temperatures above the 'melting point thereof, slowly adding thereto an aqueous solution of a saponifying alkali while evaporating water from the reacting mixture at a rate not less than the combined rate of water addition and water formation in the mixture.

2. A method of saponifying resin acids with alkaline solutions while avoiding gel formation which comprises heating said acids to temperatures above the melting point thereof and sufficiently high to ensure rapid volatilization of water therefrom and adding thereto an aqueous solution of a saponifying alkali at a rate such that the water content of the reaction mixture does not exceed 5% at any time.

3. A method of saponifying resin acids with alkaline solutions while avoiding gel formation which comprises heating said acids to temperatures well above the melting point thereof, slowly. adding thereto an aqueous solution of a saponifying alkali while agitating the mixture, evaporating water from the reaction mixture at a rate not less than the combined rate of water addition and water formation in the mixture, and also adding as a diluent a terpene which boils above about C. before completing the alkali addition.

4. A method of saponifying acids of rosin with alkaline solutions while avoiding gel formation which comprises heating said acids to temperatures above the melting point thereof, slowly adding thereto an aqueous solution of a saponifying alkali while evaporating water from the reacting mixture at a rate not less than the combined rate of water addition and water formation in the mixture.

5. A method of saponifying the acids of rosin with alkaline solutions while avoiding gel formation which comprises, melting said rosin and maintaining it in molten condition at tempera tures sufilciently high to ensure the rapid volatilization of water therefrom and adding thereto an aqueous solution of a saponifying alkali at a rate such that the water content of the reaction mixture does not exceed 5% at any time.

6. A method of saponifying the acids of rosin with alkaline solutions while avoiding gel formation which comprises adding an aqueous solution of a saponifying alkali to molten rosin at temperatures not substantially lower than 150 C. and at a rate such that the water content of the reaction mixture does not exceed 5% at any time.

7. A method of saponifying the saponlfiable matter in rosin which includes the step of heating the same to 0., adding thereto a 75% solution of caustic soda at substantially 165 C., the rate of caustic soda addition being such that the water. content does not; exceed 5% at a y time, whereby the formation of a gel lndispersi-- his in the reaction mixture is avoided', withdrawing a portion of the liquid; reaction product and solidifyingthe. same by cooling and adding to the remaining reaction productin the reaction Vessel additional quantities of molten rosin and heated" alkali in substantial-ly'the sameproper:- tions' and repeatiizig the cycle.

8, A method of saponi-fiying the acids of rosin with alkaline solutions while avoiding gel formation' which comprises continuouslymixing; moltenrosin preheated to at least 15.0? C, with an aqueous solution of a saponifying alkali at a rate suchthat thewater content of the mixture does not exceed 5% at. any time, agitating the mixture at temperature of at least 150C. until substantially all the alkali. has reacted with the rosin acids, 2 and continneusly withdrawing; finished resinaac-idsoapirom the system.

' 9., A method oi preparing; a dryrosin size. which comprises; heating acids of rosin ta temperatures well above 1 the melting point thereof, slowly adding thereto an. aqueous solution ot a saponify-ing alkali while evaporating water from therea-ction mixture at a rate not, less than the combined; rate of water addition and water formatiqn in the mixture, agitating the mixture at, elevated temperatures above the solidification point thereof until substantially all} the alkali has reacted with the rosin acids and a product containing less than 5% of water is obtained, and

rapidlycoolingthe productin flaked form by passing it in thin films over arr artificially cooled moving sunfacel GEORGE H. FQSTER.